As the main equipment to provide low temperature environment of space infrared load, the multi-directional micro-vibration of mechanical cryocooler is an important factor affecting the image quality of large aperture and high resolution space telescope and the stability of superstable cavity in atomic optical clock system. According to the multidirectional vibration characteristics of cryocooler, a multi-directional active vibration control method based on the principle of adaptive narrowband filter is proposed, and a multidirectional adaptive active vibration reduction system is built. The experimental results show that this method can effectively suppress the multi-directional micro-vibration of the cryocooler, and the high order vibration acceleration of the compressor in the axial direction, the tube direction and the vertical bottom plate direction is reduced to the order of 1E–4 g.

Objective Mechanical cryocoolers are widely used in fields such as space-based astronomical observation and low-temperature infrared detection. The reciprocating motion of the compressor piston and the internal airflow pulsation of the cryocooler are the main reasons for the multi-directional vibration of the cryocooler. Micro vibrations can cause visual axis jitter in optical systems, reducing stability accuracy. In optical clock systems, vibrations directly affect the stability of the low-temperature ultra stable cavity length, thereby affecting the stability of laser frequency. There are already various control methods for micro vibration disturbances in cryocoolers. In recent years, the suppression of multi-directional vibration in cryocoolers has mainly been achieved through passive vibration isolation or a combination of active and passive vibration control methods. However, passive vibration isolation, due to structural limitations, may bring additional problems such as in orbit unlocking. Therefore, based on the adaptive narrowband filter control method, this article designs a multi-directional adaptive active vibration reduction system for cryocoolers.

Methods This article compares two different active vibration reduction methods (Tab.1), selects external actuators as the active damper, conducts dynamic analysis of the system to determine the installation position of the active damper (Fig.5), proposes a multi-directional active vibration control method based on the principle of adaptive narrowband filter, and establishes an adaptive active vibration reduction model (Fig.6). Finally, a multi-directional adaptive active vibration reduction system was built (Fig.7). which consists of vibration sensors, control circuits, and dampers. Among them, the input of the control circuit is the vibration signal collected by the acceleration sensors. After being processed by an adaptive algorithm, the vibration reduction drive signal is output to the external actuators, generating a multi-directional vibration force that cancels out the original vibration force.

Results and Discussions Adopting the adaptive active vibration reduction method, a multi-directional adaptive active control system testing platform for cryocooler was built (Fig.8). Perform vibration analysis on the three directions of the cryocooler, namely axial (x), pipe connection direction (y), and vertical bottom plate direction (z) (Fig.9). After vibration reduction, the second, third, and fourth order vibrations in the x direction decreased from 0.001 34 g, 0.002 77 g and 0.001 54 g to 0.000 08 g, 0.000 1 g and 0.000 1g, respectively; The y direction high-order vibration decreased from 0.001 72 g, 0.000 85 g and 0.000 06 g to 0.000 17 g, 0.000 03 g and 0.000 05 g, and the z direction high-order vibration decreased from 0.005 71 g, 0.002 22 g, 0.000 57 g to 0.000 17 g, 0.000 19 g and 0.000 13 g. The overall additional power consumption of the three damping actuators was less than 1.5 W.

Conclusions Three active vibration reduction methods using external actuators were proposed by comparing different active vibration reduction methods. A multi-directional adaptive active vibration reduction model was established, and a multi-directional vibration reduction testing system for cryocoolers was built to verify the model's effectiveness. The experimental results show that after multi-directional vibration control, the acceleration of high-order vibrations in the x, y, and z directions of the compressor is reduced to the order of 1E–4 g, providing technical support for the research and application of multi-directional adaptive active vibration reduction methods for cryocoolers.